[PATCH 2/2] csky: add CONFIG_CPU_HAS_MATHEMU and use in traps

From: Wang Junqiang
Date: Tue Apr 20 2021 - 22:59:35 EST

This patch contains the use of fpu instruction emulation by trap_c.
It defined _fcr, _fesr for user space in ptrace.h which is used in fpu.c
and instruction emulation. During initialization, all fpe are enabled,
and the configuration that read/write fcr and fesr in glibc library is captured
when privilege exception is triggerd by mfcr and mtcr < ,15>.

steps:
1.enable all fpe interrupts
2.mfcr/mtcr trigger privilege exception
3.synchronize fcr and fesr of user app through fpu_libc_helper function
4.fpe interrupt at runtime
5.fpu instruction simulation is based on user_fcr and user_fesr
6.clearing interrupts and synchronizing fcr fesr
7.state restore and continue running

Signed-off-by: Wang Junqiang <wangjunqiang@xxxxxxxxxxx>
Signed-off-by: Li Weiwei <liweiwei@xxxxxxxxxxx>
---
arch/csky/Kconfig | 8 ++++++++
arch/csky/Makefile | 1 +
arch/csky/abiv2/fpu.c | 31 ++++++++++++++++++++++++-----
arch/csky/abiv2/inc/abi/fpu.h | 9 ++++++++-
arch/csky/include/uapi/asm/ptrace.h | 6 ++++++
arch/csky/kernel/traps.c | 30 +++++++++++++++++++++++++---
6 files changed, 76 insertions(+), 9 deletions(-)

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 34e91224adc3..a414225570c1 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -97,6 +97,9 @@ config CPU_HAS_CACHEV2
config CPU_HAS_FPUV2
bool

+config CPU_HAS_MATHEMU
+ bool
+
config CPU_HAS_HILO
bool

@@ -281,6 +284,11 @@ config CPU_HAS_VDSP
bool "CPU has VDSP coprocessor"
depends on CPU_HAS_FPU && CPU_HAS_FPUV2

+config CPU_HAS_MATHEMU
+ bool "CPU has FPU Mathemu Instructions"
+ depends on CPU_CK810 || CPU_CK860
+ default n
+
config CPU_HAS_FPU
bool "CPU has FPU coprocessor"
depends on CPU_CK807 || CPU_CK810 || CPU_CK860
diff --git a/arch/csky/Makefile b/arch/csky/Makefile
index 37f593a4bf53..495f3a2fad6a 100644
--- a/arch/csky/Makefile
+++ b/arch/csky/Makefile
@@ -64,6 +64,7 @@ head-y := arch/csky/kernel/head.o
core-y += arch/csky/kernel/
core-y += arch/csky/mm/
core-y += arch/csky/$(CSKYABI)/
+core-$(CONFIG_CPU_HAS_MATHEMU) += arch/csky/math-emu/

libs-y += arch/csky/lib/ \
$(shell $(CC) $(KBUILD_CFLAGS) $(KCFLAGS) -print-libgcc-file-name)
diff --git a/arch/csky/abiv2/fpu.c b/arch/csky/abiv2/fpu.c
index 5acc5c2e544e..3cd17cf9319e 100644
--- a/arch/csky/abiv2/fpu.c
+++ b/arch/csky/abiv2/fpu.c
@@ -38,8 +38,11 @@ int fpu_libc_helper(struct pt_regs *regs)
return 0;

tinstr = instr_hi | ((unsigned long)instr_low << 16);
-
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ if (((tinstr >> 21) & 0x1F) != 15)
+#else
if (((tinstr >> 21) & 0x1F) != 2)
+#endif
return 0;

if ((tinstr & MTCR_MASK) == MTCR_DIST) {
@@ -53,10 +56,19 @@ int fpu_libc_helper(struct pt_regs *regs)

regx = *(&regs->a0 + index);

- if (tmp == 1)
+ if (tmp == 1) {
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ mtcr("cr<1, 2>", regx | 0x3f);
+ current->thread.user_fp.user_fcr = regx;
+#else
mtcr("cr<1, 2>", regx);
- else if (tmp == 2)
+#endif
+ } else if (tmp == 2) {
mtcr("cr<2, 2>", regx);
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ current->thread.user_fp.user_fesr = regx;
+#endif
+ }
else
return 0;

@@ -73,10 +85,19 @@ int fpu_libc_helper(struct pt_regs *regs)
if (tmp > 2)
return 0;

- if (tmp == 1)
+ if (tmp == 1) {
+#ifndef CONFIG_CPU_HAS_MATHEMU
regx = mfcr("cr<1, 2>");
- else if (tmp == 2)
+#else
+ regx = current->thread.user_fp.user_fcr;
+#endif
+ } else if (tmp == 2) {
+#ifndef CONFIG_CPU_HAS_MATHEMU
regx = mfcr("cr<2, 2>");
+#else
+ regx = current->thread.user_fp.user_fesr;
+#endif
+ }
else
return 0;

diff --git a/arch/csky/abiv2/inc/abi/fpu.h b/arch/csky/abiv2/inc/abi/fpu.h
index aabb79355013..c3509ace542c 100644
--- a/arch/csky/abiv2/inc/abi/fpu.h
+++ b/arch/csky/abiv2/inc/abi/fpu.h
@@ -9,7 +9,14 @@
int fpu_libc_helper(struct pt_regs *regs);
void fpu_fpe(struct pt_regs *regs);

-static inline void init_fpu(void) { mtcr("cr<1, 2>", 0); }
+static inline void init_fpu(void)
+{
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ mtcr("cr<1, 2>", 0x3f);
+#else
+ mtcr("cr<1, 2>", 0);
+#endif
+}

void save_to_user_fp(struct user_fp *user_fp);
void restore_from_user_fp(struct user_fp *user_fp);
diff --git a/arch/csky/include/uapi/asm/ptrace.h b/arch/csky/include/uapi/asm/ptrace.h
index 3be9c14334a6..1ffb6190686a 100644
--- a/arch/csky/include/uapi/asm/ptrace.h
+++ b/arch/csky/include/uapi/asm/ptrace.h
@@ -45,6 +45,12 @@ struct user_fp {
unsigned long fesr;
unsigned long fid;
unsigned long reserved;
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ unsigned long user_fcr;
+ unsigned long user_fesr;
+ unsigned long reserved1;
+ unsigned long reserved2;
+#endif
};

#endif /* __ASSEMBLY__ */
diff --git a/arch/csky/kernel/traps.c b/arch/csky/kernel/traps.c
index e5fbf8653a21..053a4f7dff9e 100644
--- a/arch/csky/kernel/traps.c
+++ b/arch/csky/kernel/traps.c
@@ -27,6 +27,10 @@

#ifdef CONFIG_CPU_HAS_FPU
#include <abi/fpu.h>
+#ifdef CONFIG_CPU_HAS_MATHEMU
+extern inline unsigned int get_fpu_insn(struct pt_regs *regs);
+extern inline int do_fpu_insn(unsigned int inst, struct pt_regs *regs);
+#endif
#endif

int show_unhandled_signals = 1;
@@ -186,8 +190,19 @@ asmlinkage void do_trap_bkpt(struct pt_regs *regs)

asmlinkage void do_trap_illinsn(struct pt_regs *regs)
{
- current->thread.trap_no = trap_no(regs);
+#ifdef CONFIG_CPU_HAS_FPU
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ unsigned int inst;
+
+ inst = get_fpu_insn(regs);
+ if (inst && !do_fpu_insn(inst, regs)) {
+ regs->pc += 4;
+ return;
+ }
+#endif
+#endif

+ current->thread.trap_no = trap_no(regs);
#ifdef CONFIG_KPROBES
if (kprobe_breakpoint_handler(regs))
return;
@@ -209,7 +224,16 @@ asmlinkage void do_trap_illinsn(struct pt_regs *regs)

asmlinkage void do_trap_fpe(struct pt_regs *regs)
{
-#ifdef CONFIG_CPU_HAS_FP
+#ifdef CONFIG_CPU_HAS_FPU
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ unsigned int inst;
+
+ inst = get_fpu_insn(regs);
+ if (inst && !do_fpu_insn(inst, regs)) {
+ regs->pc += 4;
+ return;
+ }
+#endif
return fpu_fpe(regs);
#else
do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->pc,
@@ -219,7 +243,7 @@ asmlinkage void do_trap_fpe(struct pt_regs *regs)

asmlinkage void do_trap_priv(struct pt_regs *regs)
{
-#ifdef CONFIG_CPU_HAS_FP
+#ifdef CONFIG_CPU_HAS_FPU
if (user_mode(regs) && fpu_libc_helper(regs))
return;
#endif
--
2.17.1